People always think that it's deadly when people throw knives at others but it takes quite a bit of luck and aim for that to happen. Shurikens are far better throwing weapon than a knife since it's pretty much a circular blade. Throwing knife, unless you are super strong, would not have the mass or the required velocity to kill at all. Injure? Probably, but most of the time it would just bruise because the pommel hit the target or the knife just bounces off the clothing. Knives are not good throwing weapons compared to things like spears or shurikens.